The present invention relates generally to shipping blocking means for preventing movement of a wheeled vehicle during shipment and, more particularly, to an apparatus for securing a heavy wheeled vehicle on the bed of a railroad flatcar.
Large mobile equipment is often transported on railroad flatcars. A heavy wheeled vehicle such as the truck illustrated in FIG. 1, which may weigh upwards of 50 tons, is seen in comparison with the standard railroad flatcar upon which it is to be transported. In order to assure retention of a wheeled vehicle on the flatcar during severe shocks or vibration occurring in transit, during abrupt starts and stops, or during humping in switching yards, it is necessary that the vehicle be firmly secured to the flatcar. Tremendous forces can be generated by such a truck while it is being transported on a railroad flatcar. For instance, during humping at 10 miles per hour, the 50-ton truck shown carried on a non-cushioned flatcar can generate a horizontal force of 315 tons. Forces are lower at slower speeds or with cushioned flatcars. The center of application of these forces occurs several feet over the bed of the flatcar along the line of the center of gravity of the truck. For the truck shown, this distance is approximately 5 feet. Hence, moments of 3.15 million foot-pounds can be generated by the truck while it is on the flatcar. These forces must be compensated for by adequately securing the truck to the flatcar so as to prevent relative motion therebetween.
In the past, it has been commonplace to employ wheel chocks to prevent forward or rearward movement of the vehicle. These wheel chocks were made of wood and nailed to the wooden bed of the flatcar. Wheel chocks so attached to the flatcar were not always permanently fixed since any great amount of force on the wheel chocks tended to pull the nails from the flatcar bed. To hold the vehicle down against the bed of the flatcar, chains extending between the vehicle and the flatcar and arranged in various configurations were utilized. The number of chains required tended to be excessive in order to adequately secure such a heavy vehicle. Even when a large quantity of chains were employed, the chains tended to be ineffective with a larger, heavier vehicle because of the tremendous loads placed on them. Abrupt starts and stops or severe shock causes chains to break, since the chains are permitted to become slack and then are pulled quickly or "snapped" to a high tension condition.
In addition, utilization of chains may be excessively costly for many applications. Placement of wheel chocks and chains involves much time and effort. Wheel chocks have to be correctly positioned and nailed down. Chains have to be individually drawn taut. With so many components, valuable time and labor is wasted during the process of shipping a vehicle. Chains and nailed down wooden chocks are also economically disadvantageous because they are not exceedingly durable and because they are easily misplaced or lost when they are detached from the vehicle or the flatcar.